Just
as geologists reconstruct the Earth's past by looking
at layers of rock, Antarctic researchers examine layers
of ancient ice to discover the secrets of polar history.

Driving hollow tubes as far as 10,000 feet below the
surface, scientists retrieve long, layered cylinders
of ice, usually about three inches in diameter. These
"ice cores" contain compounds that were in the air when
the snow that formed them originally fell, as well as
everything from dust to radioactive particles.

By analyzing the contents of ice cores, researchers
can learn a lot about the environment. Alternating bands
of light and dark ice, for instance, correspond to changes
in the seasons, and help scientists construct a year-by-year
record of changes in local climate, sea level, solar
radiation, and chemistry dating back hundreds of thousands
of years.

Ice cores from Antarctica have also recorded ecological
events that took place thousands of miles away. Some
contain evidence of a volcanic eruption that occurred
in Indonesia about 73,000 years ago, and samples taken
after 1986 showed radioactive traces from the explosion
of the Chernobyl nuclear power station in the Ukraine.

To
find out more about ice cores
follow these links to activities, information, and timelines: